Apparatus for measuring angular rotation

ABSTRACT

Relative angular rotation between two spaced areas on a rotatable member is converted to linear motion by providing a threaded engagement between two tubes each of which is connected to a respective one of said areas for rotational movement therewith. Relative rotation between the spaced areas causes relative rotation between the tubes and this is converted by the threaded engagement into axial or linear movement. This linear movement can then be converted into an electrical signal which can be registered or recorded by an electronic device. To increase the range of angular rotation which can be effectively measured, a third member is interposed between those already discussed. A threaded connection is provided between this third member and one of the first mentioned members and a pin and slot connection is provided between the third member and the other of the two first mentioned members. The pin and slot connection accommodates linear movement so that axial movement of the connections of the tubes at the spaced areas does not occur.

[54] APPARATUS FOR MEASURING ANGULAR ROTATION Inventor: Gary L.Viegelahn, Lake Linden,

Mich.

Board of Control of Michigan Technological University, Houghton, Mich.

Assignee:

[22] Filed: March 27, 1970 21 Appl. No.: 23,380

[52] US. Cl. ..73/136 A [51] Int. Cl. ..G0ll 3/10 [58] Field of'Search..73/136 A [56] References Cited UNITED STATES PATENTS 2,230,049 1/1941Klamp ..73/136 A 2,260,036 10/1941 Kuehni ..73/136 A 2,432,900 12/1947Jacobsen ..73/136 A 2,737,049 3/1956 Waugh ..73/136 A 3,084,540 4/1963Larkin ..73/136 A 3,339,405 9/1967 McDowell ..73/136 A 3,104,544 9/1963Guiot ..73/136 A 3,403,550 10/1968 Hawkins ..73/136 A FOREIGN PATENTS ORAPPLICATIONS 158,684 3/1964 U.S.S.R. ..73/88.5

3,683,685 [4 1 Aug. 15, 1972 [57] ABSTRACT Relative angular rotationbetween two spaced areas on a rotatable member is converted to linearmotion by providing a threaded engagement between two tubes each ofwhich is connected to a respective one of said areas for rotationalmovement therewith. Relative rotation between the spaced areas causesrelative rotation between the tubes and this is converted by thethreaded engagement into axial or linear movement. This linear movementcan then be converted into an electrical signal which can be registeredor recorded by an electronic device. To increase the range of angularrotation which can be effectively measured, a third member is interposedbetween those already discussed. A threaded connection is providedbetween this third member and one of the first mentioned members and apin and slot connection is provided between the third member and theother of the two first mentioned members. The pin and slot connectionaccommodates linear movement so that axial movement of the connectionsof the tubes at the spaced areas does not occur.

10 Claims, 5 Drawing Figures APPARATUS FOR MEASURING ANGULAR ROTATIONThis invention relates to arrangements for measuring angular rotationand, more particularly, to such an arrangement as can measure bothtorque in a rotatable member and relatively large amounts of angularrota- SUMMARY OF INVENTION Among the general objects of this inventionis to provide a simple and economical device which will measure angularrotation in a member or between two reference points whether the angleis small or relatively large and, moreover, one which permits use inconnection with an arrangement capable of providing a suitable read-out.

For the achievement of these and other objects, this invention proposesto connect two sensing members relative to a rotatable member such thatrotation of that member is translated into relative movement between thetwo sensing members which, depending upon the particular application,can be used as an indication of torque in the rotatable member or theamount of rotation of that member. The two sensing members can beconnected one with respect to the other and with respect to therotatable member such that torsion in or rotation of that member causesrelative rotation and axial displacement between the sensing memberswhich corresponds to the degree of torsion or amount of rotation. Inthis connection the two sensing members can be threaded together toprovide for relative rotation therebetween and consequential axialmovement, or a third member may be interposed between the sensingmembers. The third member can be threaded to one of the sensing membersand have a connection with the other, e.g. a pin and slot connection, bymeans of which the sensing members rotate relative to each other andaxial movement is accommodated in the pin and slot connection. The lateraffords the advantage of increasing the amount of relative rotationwhich can be measured without any axial movement at the areas at whichthe sensing members are connected with respect to the rotatable member.Both arrangements translate rotation into linear movement which can beused in providing a suitable read-out.

FIG. 1 is an axial section view of an embodiment of an arrangement whichconverts angular rotation into linear motion;

FIG. 2 is a perspective view of an alternative embodiment;

FIG. 3 is an axial section view of the device shown in FIG. 2;

FIG. 4 is a sectional view of another embodiment of the proposedinvention; and

FIG. 5 is a sectional view of still another alternative embodiment ofthe proposed invention.

With reference to FIG. 1, an arrangement of cylindrical tubes 2 and 4 isconnected to shaft S. The shaft is mounted for rotation and each tube isconnected to the shaft for rotation therewith, but connected at axiallyspaced areas on the shaft. More specifically, tube 2 is connected toshaft S at areaA" by set screws 6. Tube 4 is connected to shaft S by setscrews 8, but screws 8 engage the shaft at an area B which is spacedaxially from area A. Tubes 2 and 4 are joined through a threadedconnection 10.

With this arrangement, tubes 2 and 4 will rotate with shaft S but serveto sense and respond to relative angular movement between shaft areas Aand'B. By reason of threaded connection 10, such angular movement causesthe tubes to rotate relative to each other and also results in axialmovement therebetween. This axial movement is thus a measure of relativemovement between areas A" and B or, stated another way, torque in theshaft.

The arrangement of FIG. 1, although adequate for many applications, hasa shortcoming in that it is limited to measuring relatively smallamounts of angular movement. Large amounts of angular movement mayresult in axial movement to such a degree as to move the tube connectionat either area A or B, or both. Disturbing the connection can adverselyaffect the reliability of future response to angular movement or torque.

The arrangement in FIG. 2, while incorporating the features of theembodiment of FIG. 1, overcomes the aforementioned shortcoming and canbe used to measure relatively larger amounts of angular movement.

In order to convert the angular rotation between reference areas A and Bto linear movement, the embodiment of FIG. 2 includes three cylindricaltubes mounted on shaft S. An outer tube 12 is secured to shaft S atreference area A" by suitable means such as set screws 14 threadedthrough tube 12 to engage the shaft at area A. An inner tube 16 islikewise suitably fixed to shaft S at area B by set screws 18. Anintermediate tube 20 is provided between and telescopes both tubes 12and 16. Tube 20 is in threaded engagement with tube 12 and thus is freeto rotate relative to tube 12 and to move axially with respect to tube12 as a result of that rotation.

Means 22 is provided and prevents tube 20 from rotating relative to tube16 while at the same time permitting axial movement between tubes 20 and16. Means 22 is comprised of an axial slot 24 in tube 16 and a pin 26secured to tube 20 and projecting into slot 24 but not engaging shaft S.For accuracy in measurement, the width of slot 24 is close to thediameter of pin 26 to reduce to a minimum, if not completely eliminate,any lost motion between tubes 20 and 16. On the other hand, axialmovement between tubes 16 and 20 is accommodated by slot 24.

Linear motion is achieved as follows, upon twisting of shaft S, relativerotation occurs between reference areas A and B. This will causerelative rotation between tube 12 and tubes 16 and 20 considered as aunit. This occurs because tube 16 is secured to shaft S at referencearea 5", tube 16 being operatively linked to tube 20 through pin andslot connection 22. As this relative rotation occurs, tube will bethreaded into or out of tube 12 causing axial movement therebetween.Only tube 20 moves axially relative to shaft S. That is, since tube 12is secured to shaft 10, any rotation between tubes 12 and tube 20 willcause tube 20 to move axially relative to tube 12. This is permittedwithout requiring any resultant axial movement of tube 16 because of thepin and slot connection. Therefore, at all times the connections atreference areas A and B remain true with no axial movement therebetweenyet there is axial or linear movement relative to the points which canbe measured. By picking a set of reference points on tubes 12 and 20,for example points a and b shown in the drawings (or similar points ontubes 16 and 20), this resultant linear displacement can be used as ameasure of rotation between areas A" and B.

Two arrangements for converting linear motion between reference points aand b to a useable signal are shown in the drawings. The firstalternative, shown in FIG. 4, utilizes a truncated cone mounted on theouter periphery of tube 12, with the sloping cone surface 32 facingaxially towards tube 20. A cantilever beam 34 extends axially withrespect to tubes 12 and 30 and is fixed to tube 20 through mountingblock 35. A pair of strain gauges 36 are mounted on the upper and lowersurface of beam 34, the strain gauges being appropriately wired in anelectrical read-out circuit (not shown). A base position is selectedwherein the strain gauges are prestressed and provide a base orreference reading or condition of the read-out circuit. Upon axialmovement of tube 20, beam 34 will be deflected up or down on cone 30.The resultant change in resistance of the strain gauges thus provides anelectrical signal, or deviation from the base or reference reading,corresponding to the axial displacement which is in turn a directfunction of the angular rotation between reference areas A" and B. Theelectrical signal so provided can then be fed into an appropriateelectronic device for recording and/or providing a direct read-out.

An alternative arrangement for obtaining an electric signal is shown inFIG. 5. In this arrangement an annular flange 40 is connected at someconvenient point on tube 12. One possible mode of connection is to tackweld the flange around tube 12. A linear variable differentialtransformer includes coil 42 and core 44. Coil 42 is affixed to tube 20.A push rod 46 extends from core 44 to engage flange 40 and a spring 48.Spring 48 maintains engagement of push rod 46 with flange 40 so that thepush rod, and correspondingly core 44, move jointly with tube 20. Again,a neutral position is selected wherein core 44 assumes a preselectedposition within coil 42 to establish a base or reference condition of anelectric circuit (now shown) of which the coil and core are a part.Axial movement of tube 20 with respect to tube 12 will cause push rod 46to move an equal distance thereby causing core 44 to likewise move incoil 42 and change the output signal of the coil in proportion to thelinear movement of the tube. This results in an electric signalcorresponding to the linear movement, which signal is directlyproportional to the angular rotation between points A and B. Again, thissignal may be fed into an appropriate device for recording ortranslation into a direct read-out.

ples of 360without affecting accuracy or operation.

Further flexibility in use of the device is present in the embodimentsof FIG. 2-5 in that the distance between reference areas can be selectedby moving the tubes 12 and 16 axially. The length of slot 24 can bevaried as desired and thus affords wide latitude in the amount oftorque, or rotation, that can be measured.

Although the invention has been illustrated and described in connectionwith preferred embodiments thereof, it will be apparent to those skilledin the art that various changes and modifications maybe made thereinwithout departing from the spirit of the invention or from the scope ofthe appended claims.

Iclaim 1. Apparatus for measuring angular rotation between two axiallyspaced areas on a rotatable body compris ing, in combination,

first means affixed to said rotatable body at one of said areas andhaving an axial extension along said rotatable body,

second means afiixed to saidrotatable body at the other of said areasand having an axial extension along said rotatable b'ody,

third means connecting said first and second means and operative torespond to relative rotation between said first and second means as aresult of relative angular rotation between said areas and to moveaxially relative to' said first and second means by an amountcorresponding to said relative rotation between said spaced areas, and

motion sensing means including fourth means connected to one of saidfirst and second means, and

fifth means connected to said third means and adapted to moveaxially'therewith whereby said fourth and fifth means move axiallyrelative to one another in response to said angular rotation and saidrelative axial movement to generate a signal representative of thedegree of said angular rotation.

2. The apparatus of claim 1 wherein said first and second means comprisegenerally tubular members and said third means comprises a threadedconnection between said tubular members.

3. The apparatus according to claim 1 wherein said third means isconnected to said second means through means holding said third meansagainst rotation relative to said second means and providing forrelative axial movement therebetween so that said angular rotationresults in rotation of said third means relative to said first means andaxial displacement of said third means relative to both said first andsecond means.

4. The apparatus according to claim 1 wherein said first means comprisesa first cylindrical tube surrounding a portion of said rotatable body,

including means for attaching said first tube to one of said areas andwith a portion extending toward said other area,

wherein said second means comprises a second cylindrical tubesurrounding a portion of said rotatable body,

including means for attaching said second tube to said other of saidareas and with a portion extending toward said one area, and

wherein said third means includes a third cylindrical tube surroundingsaid rotatable body and being in threaded engagement with said firsttube to permit relative rotation and axial displacement therebetween,said third tube being in telescoped relationship with said second tube,

and including means connecting said second and third tubes and operativeto permit axial displacement while preventing relative rotationtherebetween.

5. The apparatus according to claim 4 wherein said motion sensing meanscomprises a cone mounted on the outer periphery of one of said threecylindrical means with the angularly sloping surface thereof facing in agenerally axial direction, a beam mounted on another of said threecylindrical means, said beam extending axially toward and engaging saidsloped surface of said cone so that axial movement of said cone or beamtowards or away from each other will deflect said beam, and at least onestrain gauge mounted on said beam so that the deflection of said beamwill produce a signal corresponding to the rotation between said areas.

6. The apparatus according to claim 4 wherein said motionsensing meanscomprises an electrical coil affixed to one of said three cylindricalmeans, a core extending into said coil, means connecting said core toanother of said three cylindrical means so that axial movement of saidone of said three cylindrical means relative to said other will causesaid core to move axially relative to said coil and change the outputsignal of the coil in accordance with the angle of rotation between saidareas.

7. The apparatus according to claim 4 wherein said last mentioned meanscomprises means defining an axial slot in one of said second and thirdtubes and a pin fixed to the other of said second and third tubes, saidpin and slot permitting said third tube and second tubes to move axiallywith respect to each other while 4 preventing relative rotationtherebetween.

8. The apparatus according to claim 7 wherein said motion sensing meanscomprises a cone having a sloping surface facing in a generally axialdirection and a beam, one of said cone and beam mounted on said thirdtube and the other mounted on one of said first and second tubes, saidbeam extending axially toward and engaging the sloped surface of saidcone so that axial movement of said cone or beam toward or away fromeach other will deflect said beam, and at least one strain gauge mountedon said beam so that the deflection of said beam will produce a signalproportional to the angle of rotation between said areas.

9. The apparatus according to claim 7 wherein said motion sensing meanscomprises an electrical coil and core, said coil connected to said thirdtube, said core connected to one of said first and second tubes andextending into said COll so that axial movement of said thirdcylindrical tube relative to said one of said first and second tubeswill cause said core to move relative to said coil'to generate a signalcorresponding to the angle of rotation between said areas.

10. Apparatus for measuring angular rotation between two axially spacedareas on a rotatable body comprising, in combination,

first and second members threadably connected together to providerelative axial movement therebetween in response to relative rotationthereof,

means affixing said first member to one of said areas;

means connecting said second member to the other of said areas, saidconnecting means connected to and rotatable with said rotatable body andoperative to permit said second member to rotate with said rotatablebody while accommodating relative axial movement between said first andsecond members; and

motion sensing means including a first sensing member affixed to one ofsaid first and second members and a second sensing member affixed to theother of said first and second members and adapted to move axially,therewith whereby said first and second sensing members move axiallyrelative to one another in response to said angular rotation and saidrelative axial movement to generate a signal representative of thedegree of said angular rotation.

1. Apparatus for measuring angular rotation between two axially spacedareas on a rotatable body comprising, in combination, first meansaffixed to said rotatable body at one of said areas and having an axialextension along said rotatable body, second means affixed to saidrotatable body at the other of said areas and having an axial extensionalong said rotatable body, third means connecting said first and secondmeans and operative to respond to relative rotation between said firstand second means as a result of relative angular rotation between saidareas and to move axially relative to said first and second means by anamount corresponding to said relative rotation between said spacedareas, and motion sensing means including fourth means connected to oneof said first and second means, and fifth means connected to said thirdmeans and adapted to move axially therewith whereby said fourth andfifth means move axially relative to one another in response to saidangular rotation and said relative axial movement to generate a signalrepresentative of the degree of said angular rotation.
 2. The apparatusof claim 1 wherein said first and second means comprise generallytubular members and said third means comprises a threaded connectionbetween said tubular members.
 3. The apparatus according to claim 1wherein said third means is connected to said second means through meansholding said third means against rotation relative to said second meansand providing for relative axial movement therebetween so that saidangular rotation results in rotation of said third means relative tosaid first means and axial displacement of said third means relative toboth said first and second means.
 4. The apparatus according to claim 1wherein said first means comprises a first cylindrical tube surroundinga portion of said rotatable body, including means for attaching saidfirst tube to one of said areas and with a portion extending toward saidother area, wherein said second means comprises a second cylindricaltube surrounding a portion of said rotatable body, including means forattaching said second tube to said other of said areas and with aportion extending toward said one area, and wherein said third meansincludes a third cylindrical tube surrounding said rotatable body andbeing in threaded engagement with said first tube to permit relativerotation and axial displacement therebetween, said third tube being intelescoped relationship with said second tube, and including meansconnecting said second and third tubes and operative to permit axialdisplacement while preventing relative rotation therebetween.
 5. Theapparatus according to claim 4 wherein said motion sensing meanscomprises a cone mounted on the outer periphery of one of said threecylIndrical means with the angularly sloping surface thereof facing in agenerally axial direction, a beam mounted on another of said threecylindrical means, said beam extending axially toward and engaging saidsloped surface of said cone so that axial movement of said cone or beamtowards or away from each other will deflect said beam, and at least onestrain gauge mounted on said beam so that the deflection of said beamwill produce a signal corresponding to the rotation between said areas.6. The apparatus according to claim 4 wherein said motion sensing meanscomprises an electrical coil affixed to one of said three cylindricalmeans, a core extending into said coil, means connecting said core toanother of said three cylindrical means so that axial movement of saidone of said three cylindrical means relative to said other will causesaid core to move axially relative to said coil and change the outputsignal of the coil in accordance with the angle of rotation between saidareas.
 7. The apparatus according to claim 4 wherein said last mentionedmeans comprises means defining an axial slot in one of said second andthird tubes and a pin fixed to the other of said second and third tubes,said pin and slot permitting said third tube and second tubes to moveaxially with respect to each other while preventing relative rotationtherebetween.
 8. The apparatus according to claim 7 wherein said motionsensing means comprises a cone having a sloping surface facing in agenerally axial direction and a beam, one of said cone and beam mountedon said third tube and the other mounted on one of said first and secondtubes, said beam extending axially toward and engaging the slopedsurface of said cone so that axial movement of said cone or beam towardor away from each other will deflect said beam, and at least one straingauge mounted on said beam so that the deflection of said beam willproduce a signal proportional to the angle of rotation between saidareas.
 9. The apparatus according to claim 7 wherein said motion sensingmeans comprises an electrical coil and core, said coil connected to saidthird tube, said core connected to one of said first and second tubesand extending into said coil so that axial movement of said thirdcylindrical tube relative to said one of said first and second tubeswill cause said core to move relative to said coil to generate a signalcorresponding to the angle of rotation between said areas.
 10. Apparatusfor measuring angular rotation between two axially spaced areas on arotatable body comprising, in combination, first and second membersthreadably connected together to provide relative axial movementtherebetween in response to relative rotation thereof, means affixingsaid first member to one of said areas; means connecting said secondmember to the other of said areas, said connecting means connected toand rotatable with said rotatable body and operative to permit saidsecond member to rotate with said rotatable body while accommodatingrelative axial movement between said first and second members; andmotion sensing means including a first sensing member affixed to one ofsaid first and second members and a second sensing member affixed to theother of said first and second members and adapted to move axially,therewith whereby said first and second sensing members move axiallyrelative to one another in response to said angular rotation and saidrelative axial movement to generate a signal representative of thedegree of said angular rotation.